Civil Code, Art. 1678

If the lessee makes, in good faith, useful improvements which are suitable to the use for which the lease is intended, without altering the form or substance of the property leased, the lessor upon the termination of the lease shall pay the lessee one-half of the value of the improvements at that time. Should the lessor refuse to reimburse said amount, the lessee may remove the improvements, even though the principal thing may suffer damage thereby. He shall not, however, cause any more impairment upon the property leased than is necessary. With regard to ornamental expenses, the lessee shall not be entitled to any reimbursement, but he may remove the ornamental objects, provided no damage is caused to the principal thing, and the lessor does not choose to retain them by paying their value at the time the lease is extinguished. (n)